With overwhelming numbers, police took over Cairo locations designated by organizers as gathering points, checking IDs and turning potential protesters away under the threat of arrest.
At least 100 protesters had been arrested by nightfall, mostly in the Dokki district in Cairo's twin city of Giza, according to activists and rights lawyers.
The Press Syndicate said a total of 11 journalists were arrested during the course of the day and that all but one were released hours later.
"The minute we started gathering they attacked us and we fled," said another protester from the impoverished and densely populated Cairo district of Nahya.
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Both protesters requested anonymity because they feared reprisals.
Fearing another round of unrest after years of turmoil, some city residents and shopkeepers were hostile toward the protesters today.
"The sons of dogs want to bring down the state," shouted one el-Sissi supporter as he watched police beat up two protesters.
Determined to prevent the protests, police took up positions early today in Cairo's Tahrir Square, the epicenter of the 2011 uprising, and deployed on the city's ring road, downtown and at a suburban square where hundreds of Islamist protesters were killed when security forces broke up their sit-in in August 2013.
Today's arrests followed the detention in recent days of scores of activists in pre-dawn house raids and downtown cafe roundups as authorities sought to derail plans for the demonstrations.
Rights groups say as many as 100 have been arrested since late last week, with some picked up by police just hours before today's protests were due to start.